As background, numerous administering devices are known for dispensing fluids such as, for example, medicaments like insulin, hormone preparations, or other medical or cosmetic substances. With most of these devices, especially if dispensing is performed via a needle coupled to the distal end of the ampoule or device, the fluid is dispensed by a linearly guided plunger. Particularly in the case of low basal rates, static friction problems can occur due to the fact that the stopper or plunger causing the dispensing action (e.g., driven by a plunger rod) also assumes a sealing function and is made from a rubber-like material. In situations where this stopper or plunger is driven forward in a purely linear sliding action, a change between static friction and sliding friction repeatedly occurs between the plunger and the internal wall of the ampoule. This may cause the plunger to exhibit delayed and/or jerky movement when dispensing the fluid. As a result, uniform or consistent dispensing of the fluid from the ampoule unit is not always guaranteed.